The popularity of interactive screens has been increasing since the introduction of smart phones and tablet PCs (personal computers). Interactive screens are becoming larger in size, and there is an increasing demand on the responsiveness, resolution and intelligence of these interactive screens. Generally, an interactive screen functions by scanning each sensor, often called a node, on the screen periodically to detect the location(s) where the sensor has been activated. A sensor may be activated by direct physical contact by an object (e.g human finger or a stylus), by objects in proximity to a sensor or by stimulating a sensor from a distance.
The number of sensors activated on an interactive screen at a particular time is relatively small when compared to the number of sensors on the interactive screen. FIG. 3 shows an example of the sparse characteristics of contact made with an interactive screen. In the example shown in FIG. 3, capacitance changes on active nodes when fingers are in close proximity with the interactive screen. At locations on the interactive screen where fingers are not in close proximity with the interactive screen, the capacitance does not change.
One method of determining when sensors on an interactive screen are activated is to periodically scan all of the sensors on the screen to monitor which sensors have been activated and which sensors have not been activated. A full scan (i.e. scanning all of the sensors on the screen) may be time consuming and may consume more power than is necessary. Power consumption on portable electronic devices is critical because the amount of power may be limited. The amount of power used to drive an interactive screen may be reduced by reducing the sensing complexity of an interactive screen while maintaining the accuracy of the detection and localization of where sensors are activated.